Edit: There is also a book called Art and Craft of Problem Solving which is unrelated to this series but which is worth checking out too, despite the fact that it is not exactly what you are looking for.
Highly recommend this - it not only teaches you the math but does it in a fun fashion. The online forums are a great place too. Definitely gave me more math than my high school offered back in the days.
Edit: There is also a book called Art and Craft of Problem Solving which is unrelated to this series but which is worth checking out too, despite the fact that it is not exactly what you are looking for.